Many engines utilize compressors in the intake system to provide boost to the engine to increase the pressure in the combustion chamber, thereby increasing the power output of the engine. Some engines also utilize an exhaust gas recirculation (EGR) loop to reduce emission from the engine and/or improve fuel economy. The EGR loop can be either “high pressure” (HP) where the EGR is taken before the turbine and injected after the compressor, or “low pressure” (LP) where the EGR is taken after the turbine and injected before the compressor. For both scenarios, the compressor and the EGR loop increase the temperature of the intake air provided to the cylinders, thereby reducing the density of the air provided to the cylinder. As a result, the combustion efficiency is decreased. To decrease the temperature of the intake air charge air coolers may be positioned in the intake system. In some engines, the charge air cooler may be positioned in a conduit downstream of the compressor and upstream of a throttle as part of the front end cooling module as the charge air cooler is typically air cooled. In other applications, the charge air cooler may be water cooled and mounted in the engine compartment. Recently, advances have been made to incorporate the charge air cooler into the intake system. For example, US 2013/0220289 discloses an intake system including a plenum and throttle body with a charge air cooler integrated within the plenum. The integration of the charger air cooler into the intake system enables the overall compactness of the intake system to be increased while providing charge air cooling to intake air. Further, US 2012/0285423 discloses an integrated charge air cooler intake system which includes static seals to ensure the effectiveness of the charge air cooler.
Additionally, condensate may form within the integrated charge air cooler (CAC) when the ambient air temperature decreases, or during humid or rainy weather conditions, where the intake air is cooled below the water dew point temperature. Further, when the charge air entering the CAC is boosted (e.g., an induction pressure and boost pressure are greater than atmospheric pressure), condensate may form if the CAC temperature falls below the dew point temperature. As a result, condensate may collect at the bottom of the CAC, or in the internal passages of the CAC. When torque is increased, such as during acceleration, increased mass air flow may strip the condensate from the CAC, drawing it into the engine and increasing the likelihood of engine misfire and combustion instability.
Other attempts to address engine misfire due to condensate ingestion involve avoiding condensate build-up by incorporating a bypass for charge air to flow around the CAC. However, the inventors herein have recognized potential issues with such methods. Specifically, it may not be possible to incorporate such bypass passages into the integrated CAC system described above. For example, adding a bypass passage may require extra tubing and valves outside of the integrated CAC and intake plenum, thereby defeating the purpose of an integrated CAC that reduces engine packaging space.
In one example, the issues described above may be addressed by an engine intake assembly comprising a plenum having an integrated charge air cooler (CAC), a first header seal positioned around a circumference of a first CAC header, and a first rotatably movable seal positioned in a bypass passage defined between sides of a CAC body and the plenum and interfacing via sliding contact with the first header seal, the first movable seal varying airflow through the bypass passage. As one example, the plenum may be coupled between a compressor and an engine. Additionally, the first movable seal may be adjustable between a first position where charge air flowing through the plenum flows through the bypass passage and at least partially bypasses the CAC and a second position where charge air flowing through the plenum flows through the CAC and not the bypass passage. In both the first position and second position, the first movable seal may remain in sealing contact with the first header seal and a second header seal positioned around a circumference of a second CAC header, the second CAC header at an opposite end of the CAC from the first CAC header. Further still, an engine controller may actively adjust the first movable seal into the first position or the second position responsive to charge air temperature. In this way, CAC condensate in an integrated CAC and intake plenum may be reduced while maintaining a compact engine arrangement and adequate sealing of the CAC within the plenum. Maintaining sealing between the CAC and plenum may also reduce air leaks and increase CAC efficiency.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.